In a case where a HDTV broadcast (high-definition moving picture information) of multiplexed video and audio data in accordance with MPEG-2 TS (Transport Stream) is made in digital broadcasting using a communication line such as the Internet, the required transfer rate is high (e.g., equal to or higher than 24 Mbps) and, therefore, reducing the transfer rate by deleting information (such as null packets) not relating directly to the contents is conceivable.
In the case of MPEG-2 TS transmission at a fixed bit rate (CBR: constant bitrate), timing synchronization on the receiving side is possible in a model of transmission at a constant rate in an environment free from the influence of jitter or packet loss. If in this model the average rate is reduced simply by deleting null packets, receiving transmitted information in correct timing synchronization is difficult.
In such circumstances, a method in which MPEG-2 TS packets are converted into MPEG-2 TTS (Time-stamped Transport Stream) packets by attaching a time stamp to each of the MPEG-2 TS packets and null packets are thereafter removed has been proposed (see, for example, Patent Literature 1). Timing can be accurately synchronized on the receiving side by means of the time stamps in the MPEG-2 TTS, thereby enabling deletion of null packets on the transmitting side. The average rate of data transfer through the communication line can thereby be substantially reduced.